The purpose of this project is to allow the principal investigator time to gain a through training in basic medical research so that he can become a productive independent investigator with special interests in the prolactin isoforms. The training phase includes 1) course work and seminars in molecular biology, cell biology, endocrinology, protein biochemistry, and correlations between basic medical research and clinical practice; 2) laboratory training in cell culture, protein isolation, protein iodnation, bio- and radioimmunoassay of hormone, and monoclonal antibody development. The principal investigator also expects to complete two preprojects during this phase: 1) large scale isolation of each of the isoforms of prolactin, and 2) the thorough characterizaton of quantitative assays for them. In the second phase of this project, the principal investigator will apply what he has learned in the first phase to study 1) the distribution of the different isoforms of prolactin in different physiological and pathological conditions; 2) the effect of nutritional factors on the regulation of secretion of the isoforms; 3) the relationship between these monomeric isoforms and the clinically studied oligomeric prolactins; and 4) the possible different roles of the isoforms in lactotroph autoregulation. Phase I will be under the co- sponsorship of Dr. Ameae Walker, whose area of research is prolactin endocrinology, and Dr. Richard Luben, whose research focuses on the mechanism of hormone action. Phase II will continue to include guidance from Drs. Walker and Luben, but will also include additional input from Dr. Anthony Norman, whose area of research includes effects of nutritional factors, most particularly vitamin D, on hormone regulation. Promotion from phase I to II will be a committee decision based on course and laboratory performance and the production of a comprehensive research proposal for phase II.